The space available in an automobile for installing a heating, venting and air cooling system is generally rather limited. Often, a centrifugal blower is used for circulating air, particularly to achieve a desired quiet operation. A space-saving construction of such a blower is achieved if the air is drawn directly into the blower at an intake positioned in a blower housing wall opposite the wall to or on which an electric blower motor is mounted. However, in such a construction it is difficult to adequately cool the blower motor itself.
German Patent Publication DE 195 47 674 A1 discloses a radial blower, particularly for heating and air-conditioning systems for automobiles. In the known blower, a fan wheel driven by an electric blower motor is encased in a spiral housing section. The housing has a suction air inlet opening into a suction chamber and an air outlet leading to the outside. A closed portion of the housing opposite the air inlets has a shell-shaped recess in which at least a portion of the electric blower motor is arranged. The other portion of the electric blower motor is arranged within a shell-shaped and vaulted carrier or fan disk that connects a hub of a fan wheel with its fan ring. The fan ring supported by the carrier or fan disk has first fixed blades (31) arranged at the radial outer run of the carrier or fan disk and extending axially and radially outwardly of the electric blower motor. Second fixed blades (41) are positioned on a smoothly formed, closed inner surface facing the motor for diverting a cooling air flow from a main air flow, into the spiral housing for cooling the electric blower motor. The known radial blower brought some improvement in the cooling of the blower motor, relative to the then known art. However, especially during extended operation, the components become too hot, which has a negative effect on the service life of the blower motor.
U.S. Pat. No. 4,470,753 (Witzel--September /1984), corresponding to German Patent Publication DE 2,939,385 discloses an improved cooling of the electric motor by a radial blower in a housing having an air intake opening on its front side and a drive motor for a fan wheel on its rear side. The fan wheel has a fan ring with fan blades on a hub. A shell-shaped curved fan disk connects the fan ring to the hub. The fan disk is provided with openings through which motor-cooling air is drawn into the intake side of the fan wheel, thereby achieving good cooling of the electric motor. However, there is room for improvement.
German Patent Publication DE 34 27 565 C2 also discloses a radial blower with a radial fan driven by an electric motor. A fan disk is provided with axially outwardly extending fan blades arranged on the radial outer area of the disk. The fan disk has openings through which the cooling air which has been warmed by the electric motor, is drawn to the intake or suction side of the fan wheel, mixed with the inflow air, and diverted into the spiral delivery chamber. This fan wheel, however, is less suitable for applications that require quiet operation because the openings in the fan disk allow "short-circuit" flow between the pressure side and the suction side and, thus, the blower tends to be noisy.